Endocrine Abstracts

MNR has previously been shown to raise BP in the offspring. In rat models of protein restriction the size of the difference reported depends on the measurement method used, with telemetry reporting a smaller increase than tail cuff. Tail cuff measurements have found that global MNR increases BP but this has yet to be tested using telemetry. Evidence suggests that MNR affects offspring glucocorticoids and it is known that corticosterone is involved in the hypertension seen following maternal protein restriction. This study aimed to test whether global MNR raised BP when measured by telemetry and whether BP effects are linked to alterations in glucocorticoid levels.

Methods

Long-Evans rats were randomly allocated on day of mating to either an ad libitum fed control group (n=6) or an MNR group (n=8) that was fed 50% of the amount eaten by the controls throughout pregnancy. From birth all animals had free access to food. At ten weeks of age a male rat from each litter was implanted with a transmitter. Following recovery BP was measured over 24 hours and blood samples taken. Plasma corticosterone concentrations were assayed by EIA.

Results

MNR animals had significantly lower 24 hour BP (92.6±1.4 vs 97.6±1.5 mmHg; p<0.05) but their corticosterone levels were significantly higher (124.5±5.8 vs 101.6±1.6 ng/ml; p<0.05) than those of controls.

Conclusions

The reduction in BP is unexpected given previous findings but could be explained by the fact that these animals were not restrained and BP was measured continuously over a 24 hour period. Raised corticosterone would normally increase BP so these findings suggest that the regulatory mechanism linking BP with corticosterone has been disrupted by MNR.